What the government could buy with its $4 trillion

President Barack Obama signs the bipartisan budget bill in the Oval Office of the White House, November 2, 2015.

President Barack Obama sent his more than $4 trillion budget for fiscal 2017 to Congress on Tuesday. It's the last budget Obama will deliver as president, and is likely to be contentious as he tries to shore up a two-term legacy and congressional Republicans vie to create gridlock going into the November elections.

We're sure to hear the same talk about spending on small business and the importance of national security, but why not live a little and buy some businesses? We thought we'd help out and make some suggestions for the president, who must be getting tired of making budgetary decisions after seven years in office.

At $4.1 trillion, the U.S. has the largest federal budget in the world in terms of expenditures

If the government wanted to buy companies instead of pay for all the departments and agencies it currently supports, it could acquire more than half of the S&P 500. The $4.1 trillion budget could buy the 342 smallest companies by market capitalization. That includes brands like Kellogg, Pepco Holdings and Sysco.

If it were interested only in the big boys, it could buy the top 13 companies of the index: Apple through Wal-Mart.

On the revenue front, the U.S. is also in the lead in terms of receipts and total deficit. The deficit alone could buy 86 companies in the S&P.

That revenue tops each individual company in the S&P 500, and by a lot. You'd have to combine the annual sales of the top 26 companies to match it. That's everything from Wal-Mart to Wells Fargo.

By budget line, the Agriculture Department gets about $150 billion, putting it in line with auto companies like General Motors and Ford in revenue. The Fish and Wildlife Service, which is within the Department of the Interior, has a budget request of around $2.9 billion, making it about the size of Urban Outfitters by market cap.

As a lame duck president, Obama doesn't have much to lose and could accomplish more if he can find allies in Congress to compromise on the more moderate proposals.

Last week, it was announced that Obama would seek a $10-per-barrel tax on oil in order to raise $20 billion to fund research into alternative energy sources. With crude hovering around $30 a barrel, the extra tax could take a serious bite out of producers' incentives to drill.

If the $10-a-barrel tax had been enacted in 2015, that would bring in about $34 billion in additional revenue for the government (assuming that tax didn't force any producers to cut output), based on production figures from the Energy Information Administration. The government could buy the bottom 13 companies in the S&P with that money, a group that includes GameStop and Chesapeake Energy.

Four federal agencies have double-digit portions of the overall expenditure budget. The Department of Defense is in the news a lot for getting a sizable chunk of the budget, but it's actually smaller than Health and Human Services, Social Security and the Department of the Treasury. Its $575 billion budget (based on 2016 projections) buys a lot of F-15s, but it could also buy any company on the S&P, or the hundred smallest.

The president will also ask Congress for an extra $1.8 billion to combat the Zika virus. The disease has been spreading in South and Central America and a few cases have been found in the U.S. from people who had traveled overseas. That's a pretty small amount compared to American businesses: It's smaller than the smallest S&P company by market cap and is around the annual revenue of Red Hat, a software company based in North Carolina.

The Pentagon will ask for more than $7 billion in additional funding to ramp up the fight against the Islamic State, according to Reuters. That's a drop in the bucket of its total budget, but would be enough to buy a number of U.S. companies. The upper end would include Plum Creek Timber or retailer Bed, Bath and Beyond: Each have market caps around $7 billion.